piccolo.query.functions.array covers array_cat, array_append,
array_prepend, array_replace and array_remove, but not the && overlap
operator.

The gap it fills: "does this array contain any of these values?". Today that has
to be written as an OR of any() calls, one per value, which can't use a GIN
index. && is a single indexable test.

from piccolo.query.functions import ArrayOverlap

await Ticket.select().where(
    ArrayOverlap(Ticket.seat_numbers, [510, 511])
)

There's also a column method, matching cat / remove / append / prepend /
replace:

await Ticket.select().where(Ticket.seat_numbers.overlap([510, 511]))

Notes

• Postgres / CockroachDB only, raising the same ValueError on SQLite as the
  other array functions.
• ArrayOverlap subclasses QueryString rather than ArrayQueryString —
  ArrayQueryString overrides __add__ / __radd__ to mean concatenation,
  which doesn't apply here as && returns a boolean, not an array.
• On CockroachDB the array needs an explicit type, the same as any() /
  not_any() — the tests use QueryString("{}::INTEGER[]", [...]) for that
  reason. On Postgres a plain list works, since the type is inferred from the
  column.

Testing

Added test_overlap, test_overlap_plain_list, test_overlap_two_columns and
test_overlap_sqlite to tests/columns/test_array.py:

$ ./scripts/test-postgres.sh tests/columns/test_array.py
18 passed, 6 skipped

$ ./scripts/test-sqlite.sh tests/columns/test_array.py
12 passed, 12 skipped

I don't have a CockroachDB instance to hand, so that path is untested beyond
following the existing convention.